A stem cell treatment routinely used for bone and blood cancers is showing promise at reversing the effects of multiple sclerosis (MS).

The treatment, known as autologous haematopoietic stem cell transplant (HSCT), uses chemotherapy to break down the patient's faulty immune system. Stem cells are then harvested and re-infused into the patient to 'reboot' their immune system. Within two weeks, new red and white blood cells start to grow.

Over two million people worldwide are affected by MS. The body's own immune system attacks and damages the myelin – the protective layer that surrounds nerve fibres. This damage impairs nerve-cell transmission in the brain and the spinal cord, causing widespread disability. Although some drugs exist to help with early symptoms of the disease, there is currently no cure.

'There has been resistance to this in the pharma and academic world. This is not a technology you can patent and we have achieved this without industry backing,' Professor Richard Burt of Northwestern University in Chicago told the BBC.

This past week, the BBC documentary Panorama was given access to some of the patients treated with HSCT in a trial at the Royal Hallamshire Hospital in Sheffield.

These include Holly Dewry, who was diagnosed with MS at the age of 21. 'Within a couple of months I got worse and worse. I couldn't dress or wash myself; I didn't even have the strength to carry my daughter,' she said in the documentary.

Holly needed a wheelchair before her transplant, but after the treatment she walked out of hospital. 'It's been a miracle. I got my life and my independence back, and the future is bright again.'

Two years on she has suffered no relapses and there is no evidence of active disease on her scans.

'Ongoing research suggests stem cell treatments such as HSCT could offer hope, and it's clear that in the cases highlighted by Panorama they've had a life-changing impact,' Dr Emma Gray, head of clinical trials at UK's Multiple Sclerosis Society, told the BBC.

So far only around 20 patients have been treated with the technique for MS, but the results have been called miraculous. 'This is not a word I would use lightly, but we have seen profound neurological improvements,' Professor Basil Sharrack, a consultant neurologist at Sheffield Teaching Hospital's NHS Foundation Trust, told the Telegraph.

Doctors involved in the research stress that the treatment may not suitable to everyone with MS and results, though encouraging, are still preliminary.

The trial now aims to assess the long-term benefits of the stem cell transplant for MS. It includes patients with relapsing, remitting MS, which involves flare-ups of symptoms that can last from days to months. The international trial is being conducted at Sheffield as well as hospitals in the US, Sweden and Brazil.